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Boards Review Cards 2016 > Cytogenetics and Prenatal > Flashcards

Cytogenetics and Prenatal Flashcards

1
Q

Triploidy

A
  • 69, XXX or 69, XXY
  • 1-2% incidence in conceptions
  • 10% prevalence in miscarriages
  • Typically results in miscarriage in the first trimester, but livebirths have been reported
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2
Q

Triploidy - Digyny

A
  • Extra set of chromosomes are maternally derived

- Severe asymmetric fetal growth restriction with head sparing, small placenta

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3
Q

Triploidy - Diandry

A
  • Extra set of chromosomes are paternally derived
  • Enlarged, partially molar placenta
  • Mild fetal growth restriction
  • High NT and 10X higher maternal hCG
  • Can cause maternal early pre-eclampsia and molar pregnancy/choriocarcinoma
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4
Q

Triploidy Syndrome

A
  • Cystic placenta
  • 3,4-syndactyly
  • Unusual simian crease
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5
Q

Trisomy 13 (Patau Syndrome) Ultrasound Findings

A
  • Holoprosencephaly
  • Cystic hygroma
  • Hydrops fetalis
  • Omphalocele
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6
Q

Trisomy 18 (Edward Syndrome) Ultrasound Findings

A
  • Clenched fists
  • Choroid plexus cysts
  • Rocker bottom feet
  • Cystic hygroma
  • Omphalocele
  • Polyhydramnios
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7
Q

Trisomy 21 (Down Syndrome) Ultrasound Findings

A
  • Echogenic bowel
  • Increased NT in first trimester
  • Increased NF in second trimester
  • Cardiac defects
  • Hypoplastic nasal bone
  • EIF (weak)
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8
Q

Trisomy 21 Features

A

-Upslanted palpebral fissures
-Epicanthal folds
-Sandal gap
-BRUSHFIELD SPOTS IN IRIS
-Mild to moderate ID
-GI problems
-Hearing loss
-Hypotonia
-Short statue
-Congenital heart defects
-Hypothyroidism
-Increased risk for leukemia
-Decreased risk for solid tumors
~Occurs due to maternal or paternal MEIOSIS I non-disjunction~

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9
Q

Turner Syndrome

A 
Most common chromosomal abnormality in miscarriage
45, X
-Short stature
-Webbed neck
-Congenital heart defects - aortic stensosi
-Amenorrhea 
-Cystic hygroma
-Obesity
-Widely spaced nipples
-Learning difficulties/ADHD
-Horseshoe kidney
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10
Q

Klinefelter Syndrome

A

47, XXY

  • Tall stature
  • Hypotonia
  • Feminization at puberty: gynecomastia, broad hips, absent or reduced facial hair
  • Reduced fertility
  • Hypogonadism
  • Increased risk for breast cancer
  • Increased risk for thromboembolism
  • Normal intelligence, may have reading or speech difficulties
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11
Q

Monosomy 1p36 (1p36 deletion syndrome)

A
  • Developmental delay
  • Mild to severe ID
  • Limited or absent speech
  • Aggression and self-injurious behavior
  • Autistic behaviors
  • Dysphagia
  • Brain MRI abnormalities: Cerebral atrophy, ventricular asymmetry and/or enlargement, hydrocephalus
  • Hyperreflexia
  • Microcephaly
  • Visual problems: strabismus, cataracts, hypermetropia, nystagmus
  • Dysmorphic features: frontal bossing, small pointed chin, flat nose, deep-set eyes, thickened helices, slanting palpebral fissures, midface hypoplasia, orofacial clefting
  • Hypotonia
  • Hypothyroidism
  • Heart defects: Infantile DCM, PDA, ToF
  • Increased risk for neoplasm: neuroblastoma, prostate, lung, melanoma, hepatoma, cervical, breast, colorectal, ovarian, NHL
  • hearing loss
  • scoliosis/kyphosis
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12
Q

Trisomy 16

A

Most common TRISOMY

Always results in miscarriage/early termination

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13
Q

First Trimester Screening

A

Maternal serum levels of PAPP-A and hCG + ultrasound

ADJUSTS RISK for trisomy 18 and trisomy 21

  • Trisomy 21 shows elevated hCG and decreased PAPP-A
  • Trisomy 18 shows decreased hCG and decreased PAPP-A
  • Results can be affected by maternal age, weight, race, and gestational diabetes
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14
Q

Quad Screen/Multiple Marker Screen

A

Maternal serum levels of hCG, inhibin A, uE3, AFP

ADJUSTS RISK for trisomy 18, trisomy 21, and neural tube defects (NTD)

  • Trisomy 18 will show decreased hCG, decreased inhibin A, decreased uE3, decreased AFP
  • Trisomy 21 will show increased hCG, increased inhibin A, decreased uE3, decreased AFP
  • NTD increased risk when MoM (multiple of the median) for AFP is >2.0
  • Results can be affected by maternal age (not AFP), weight, race, and gestational diabetes
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15
Q

NIPT

A
  • Can detect some trisomies (typically 13, 18, 21, may detect others)
  • Can detect some microdeletions and microduplications
  • Can detect sex chromosome aneuploidy (to an extent)
  • May detect triploidy (SNP-based method only (Natera))
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16
Q

Ultrasound

A
  • First trimester ultrasound will measure nuchal translucency and crown-rump length
  • Second trimester ultrasound (18-20 weeks) is considered the detailed or diagnostic ultrasound
  • Will assess any structural abnormalities
17
Q

NTD Ultrasound Findings

A
  • Spina bifida – Lemon sign (Chiari II malformation), banana sign (cerebellum)
  • Anencephaly
  • Gastroschisis
18
Q

Double Bubble Sign

A

Duodenal atresia

19
Q

Amniotic Band Syndrome

A

Missing limbs or digits

20
Q

Congenital absence of the cavus septum pellucidum (CSP)

A

Septo-optic dysplasia

21
Q

Echogenic bowel

A
  • Down syndrome
  • Cystic fibrosis
  • CMV infection
  • Congenital narrowing of the bowel/bowel obstruction
22
Q

Chorionic Villus Sampling (CVS)

A
  • Diagnostic test
  • Available between 11-13 weeks gestational age
  • Samples placental tissue either transcervically or transabdominally
  • Confined placental mosaicism may be present in 1-2% of cases
  • Risk for miscarriage anywhere between 1/250 – 1/1000 depending on institution
23
Q

Amniocentesis

A
  • Diagnostic test
  • Available at or after 16 weeks gestational age
  • Samples amniotic fluid (baby pee ft. skin cells)
  • Transabdominal
  • Risk for miscarriage anywhere between 1/250 – 1/1000 depending on institution
24
Q

Imprinting

A
  • Selective silencing of paternal or maternal genes
  • Genes are silenced (imprinted) through methylation during gametogenesis
  • Paternally imprinted genes are silenced while the maternally derived copy is expressed
  • Maternally imprinted genes are silenced while the paternally derived copy is expressed
25
Q

Inversions

A

Pericentric – includes the centromere
-Can result in unbalanced offspring

Paracentric – does not include the centromere

  • Usually results in acentric fragments/dicentric chromosomes
  • Greater amounts of miscarriage
26
Q

Karyoptype

A
  • Shows an entire set of chromosomes with delineated bands
  • Useful for visualizing large deletions, duplications, translocations, and inversions
  • Resolution is too poor to detect microdeletions and duplications
27
Q

Fluorescence in situ hybridization (FISH)

A
  • Utilizes sequence complementary to the region of interest
  • Fluorescent hybridization signals euploidy or aneuploidy of the region
  • Can detect deletions >0.5-1Mb long and duplications >1 Mb long
  • Resolution is too poor for smaller deletions/duplications
  • Limited in that you must know what region to look for
  • Useful for parental studies when CMA detects a large enough deletion or duplication in a child
  • Useful for whole chromosome aneuploidy analysis (fast turnaround for trisomy 21, usually still confirmed with karyotype or CMA)
28
Q

Chromosomal Microarray (CMA)

A

Oligo-array– detects microdeletions and duplications, cannot detect balanced rearrangements such as inversions and translocations

SNP-array – detects loss of heterozygosity/regions of heterozygosity, uniparental disomy, and triploidy
-Detected by quantitative change rather than CGH

MOST clinicians will utilize a combo oligo/SNP chip to have complete coverage

Limited by interpretation of CNVs – not all are pathogenic, some VUS

29
Q

Indications for CMA

A
  • Multiple congenital anomalies not specific to a well-delineated syndrome
  • Idiopathic/non-syndromic developmental delay/intellectual disability
  • Autism spectrum disorder
  • Prenatal patients with one or more major structural anomalies on ultrasound
  • May be useful for products of conception

Boards Review Cards 2016 (29 decks)

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